Conditions
1) Place redstone in an L shape. The result should be something similar to 2014-08-13_17.48.00.png
2) Place stairs. Texture should look like something similar to 2014-08-13_17.55.52.png.

How I Found Out About It
I was trying to make a trampoline using Slime Blocks and Pistons. When I placed Redstone and Condition 1 occurred, I figured "that doesn't look normal". Looking at the stairs I had placed in a previous version, I realized redstone wasn't the only thing getting a wonky texture.